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King_Allergen Exposures and the Quest for a Healthier Home

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IAQA 18th Annual Meeting & Indoor Environment and Energy Expo (IE3) The views and opinions herein are those of the volunteer authors and may not reflect the views and opinions of IAQA. The information is offered in good faith and believed to be reliable but it is provided without warranty, expressed or implied, as to the merchantability, fitness for a particular purpose or any other matter. Allergen Exposures and the Quest for a Healthier Home Co-exposure to Allergens, Air Pollutants and Other Environmental Contaminants: Relationship With Asthma and Allergic Disease Eva M King, MSc, PhD Introduction The prevalence of asthma and other allergic diseases has been steadily increasing throughout the world over the past five decades, with a significant rise beginning in the early 1980s. The World Allergy Organization (WAO) reports that 30-40% of the population worldwide is affected by one or more allergic conditions. In the United States, approximately 54% of the population is sensitive to at least one allergy-inducing substance, according to the National Institutes of Health (NIH). A large proportion of those affected are sensitized to one or more allergens commonly found indoors. Several theories have been proposed to explain the rising trend, including the hygiene hypothesis, global warming and other climate-related factors, and changes in diet and lifestyle. Indeed, most Americans now spend nearly 90% or their time indoors where many air pollutants are 2- 5 times higher than outside levels. Recent studies suggest the importance, and perhaps requirement, of co- exposure to indoor allergens and air pollutants in the development of allergic disease. An allergen is any substance that causes an allergic reaction, typically by inhalation, ingestion, or skin contact (absorption). There are no common biological or structural characteristics that define an allergen, although they are typically either proteins or glycoproteins. Allergens are derived from a variety of animals and plants, and are named by the first three letters of the source genus followed by a single letter for the species and a number denoting the chronologic order of allergen identification. Thus, the abbreviated nomenclature for the dust mite Dermatophagoidespteronyssinus allergen 1 is Der p 1, and the major cat allergen (Felisdomesticus) is Fel d 1. Most allergens are soluble and capable of penetrating the body's protective barriers, allowing them to engage the immune system. Initial exposure to an allergen can stimulate production of IgE antibodies that recognize the allergen. Repeated exposure may lead to an allergen-specific IgE mediated immune response, causing a variety of symptoms that includes sneezing, itchy and watery eyes, rashes, or potentially life- threatening anaphylactic shock. The process of developing a physiological response to allergen exposure is called sensitization. Sensitization to indoor allergens is a major risk factor for the development and exacerbation of asthma and allergic disease (Salo et al. 2008). For most of the common indoor allergens, scientific studies have established exposure levels that are associated with increased risks of sensitization. However, the risk of sensitization varies by individual and may be influenced by several factors, including age and family history, allergen exposure patterns, geographical relocation, and co-exposure to microbial components and air pollutants. Air pollution is known to aggravate asthma and other respiratory conditions, but there is mounting evidence to support a causative relationship between air pollution exposure and sensitization to airborne allergens. While many studies have investigated allergen exposure as a single cause of health effects in allergic patients, recent studies have focused on the interaction between multiple components and factors that can be present in the indoor environment and impact the health of inhabitants.

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